Device for applying vapor retarder

ABSTRACT

A device for applying a vapor retarder film onto purlins on a roofing system has a base with rollers and guides for directing the base across the purlins. The base has a fore end and an aft end with a pair of side members. The base moves across the purlins such that the side members remain in a fixed spaced apart relationship wider than the spacing between the pair of purlins. A vertical member attached to each of the side members provides a means for mounting a web of the vapor retarder film on a roll above the base and the adjacent pair of the spaced apart purlins. Adhesive is dispensed onto the edges of the web and the web is payed out and guided onto the purlin so that the edge of the web having the adhesive is put into adhesive engagement with the top surface of the purlins and the film sealingly spans the interval between the adjacent purlins. By use of. a plurality of these devices acting in parallel, a method of applying the web to the roof purlins is taught.

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 09/419,474, filed Oct. 15, 1999 and currentlypending, which is a division of U.S. patent application 08/933,723,which issued as U.S. Pat. No. 5,968,311 on Oct. 19, 1999.

[0002] The present invention relates to a device for applying a sheet ofvapor retarder material to a roof support as a step in the placement ofa roof on a structure. More particularly, the invention relates to adevice which rides upon a pair of adjacent roof purlins, places anadhesive directly upon the top of the roof purlins, and places a vaporretarder sheet which spans the intervening space between the purlinsonto the adhesive. More particularly, the present invention relates to adevice wherein the roll bearing the vapor retarder is not on the device.Instead, the roll travels directly on the purlins and provides forwardimpetus or thrust to the device.

BACKGROUND OF THE ART

[0003] The method of applying a vapor retarder sheet or the like as onestep of applying a roofing system is described in full detail in U.S.Pat. No. 4,736,552, which issued on Apr. 12, 1988 to Lonnie R. andCherryl A. Ward, and that patent is incorporated by reference as iffully recited herein. The Ward '552 patent teaches a roof system andmethod of fabricating, as used on a building with a plurality ofparallel and spaced apart elongated structural support units defining alongitudinal surface exposed from above. The spacing between thesestructural support units is generally consistent across the longitudinalsurface. A first step in applying a roof to this type of structureinvolves securing a flexible, generally moisture impervious sheet overthe longitudinal surface to act as a vapor retarder between the buildinginterior and exterior. The method as described in Ward '552 involvesplacement of a double-faced adhesive tape along the top surface of thesupport units and then applying lengths of the sheet material as payedoff of rolls thereof atop the doubled faced adhesive tape which are onadjacent support units. The sheet material applied is sufficiently wideto cover the adjacent top surfaces and the intervening spacetherebetween. By applying a second piece of the double-faced adhesivetape over a vapor retarder sheet atop the first piece of double-facedadhesive tape, an adhesive surface for placement of an overlapping sheetof the vapor retarder material is provided. In this manner, a continuousuninterrupted surface of the vapor retarder material is secured to thetop surface of the support units. Although the Ward '552 patent teachesthe method of applying such a roofing system and also the roofing systemachieved as a result of the method, it does not teach a device foraccomplishing the step of adhering the vapor retarder to the roofsupports.

SUMMARY OF THE INVENTION

[0004] Accordingly, it is an object of the present invention to providea device for adhering a sheet of vapor retarder material spanning theintervening space between the pair of roof supports, using a line ofadhesive which has been placed onto an edge surface of the webimmediately before engaging the web surface to the roof support. Thisand other objects of the invention are provided by a device for applyinga vapor retarder film atop a pair of adjacent parallel spaced apartpurlins having a top surface in a roofing system having a plurality ofthe purlins with an interval between the purlins. The device comprises abase with a fore end and an aft end. A pair of side members are a partof the base and the base is provided with a means for moving it alongthe length of the pair of purlins such that the side members are in afixed spaced apart relationship wider than the spacing between the pairof purlins. The device further has a vertical member attached to each ofthe side members, with a means for mounting a web of the vapor retarderfilm on a roll above an adjacent pair of the spaced apart purlins. Thedevice has a means for dispensing a continuous line of adhesive along anedge of a surface of the web of vapor retarder film and a means forpaying out and guiding the vapor retarder film such that the edge havingthe line of adhesive is in adhesive engagement with the top surface ofthe purlins and the film sealingly spans the interval between theadjacent purlins.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] In the accompanying drawings, in which identical parts areidentified by identical reference numerals and in which:

[0006]FIG. 1 is a side elevation view of a first embodiment of thedevice of the present invention;

[0007]FIG. 2 is a top plan view of the first embodiment device of thepresent invention;

[0008]FIG. 3 is a top plan view of three of the first embodiment devicesof the present invention placing vapor retarder web on a roof surface;

[0009]FIG. 4 is a side elevation view of a second embodiment device ofthe present invention; and

[0010]FIG. 5 is a top plan view of the second embodiment device.

DETAILED DESCRIPTION OF THE DRAWINGS

[0011] In a roofing system as shown in FIG. 1 of Ward '552, a pluralityof purlins are provided in parallel equally spaced-apart relationship todefine a generally planar surface for the placement of a roofing systemthereupon, with an intervening space between adjacent purlins. In atypical application, these purlins are about 2.5 inches wide and arespaced about 60 inches apart, as measured center to center. AlthoughWard '552 describes the steps in applying the roofing system, thatpatent is silent as to the preferred technique or device used in theapplication of a vapor retarder sheet atop the purlins which spans theintervening space between the adjacent purlins, and the implication isthat a manual technique is used. It will be readily understood that thepresent invention device will achieve this purpose and that it hasapplication to a variety of roofing systems and the width of the purlinsand their spacing may be accommodated by variations in the device.

[0012] In the method as described by Ward '552, a vapor retarder sheetis typically laid down in strips parallel to the plurality of parallelspaced apart purlins of a roofing system, after which blankets of aninsulation layer are placed atop the vapor retarder in a juxtaposedtransverse manner. This insulation layer is then covered by the roofingsurface, which is generally laid in the same direction as theinsulation. The device of the present invention operates to lay thevapor retarder in the same direction, with the insulation and roofingsurface being laid transverse to the vapor retarder.

[0013] The device of one aspect of the present invention is shown inFIGS. 1-3; FIG. 1 showing a side elevation view from the right side ofthe device; FIG. 2 showing a top plan view and FIG. 3 showing aplurality of the devices in use on a roofing surface applying a vaporretarder web. The device 10 comprises a base 12 which is preferablyrectangular and which has a width sufficient to span a pair of spacedapart purlins, and, in fact, to extend outwardly beyond the edges of thepurlins. The base 12 having this rectangular shape has a pair ofparallel side members 14, 16 which are positioned parallel to theadjacent purlins upon which the device 10 will be moved. Connecting theside members 14, 16 are at least two cross members 18, which hold theside members in their parallel spaced apart position. Although the crossmembers 18 will be located either slightly above the top surface of thepurlins or will actually rest upon the top surface, the side members 14,16 may have a portion pending below the top surface, so that the centerof gravity of the device is kept low. In the preferred embodiment ofthis aspect of the present invention, each of the side members 14, 16has a vertical member 22 affixed thereto in a position which issubstantially normal to the side member. While the preferred method ofaffixation is direct welding of the vertical member 22 to the sidemember 14 or 16, the affixation may also be assisted by the use of acollar (not shown) which is affixed to the side members 14, 16 andreceives a first end of the vertical member 22. The use of such a collarpermits the device 10 to be assembled and broken down easily, which maybe very advantageous, since the devices are moved from one site toanother often and will need to be lifted from the ground to the roof foruse. The vertical members 22 on the side members 14, 16 are inalignment, so that a straight line between them would be perpendicularto the longitudinal axes of the purlins they straddle. If the verticalmembers are mounted in collars, it would be quite desirable to use avertical member with a rectangular or other non-circular polygonalcross-section to eliminate rotation of the cross member, but this is notrequired when the vertical members are affixed to the side memberspermanently, as by welding.

[0014] Each vertical member 22 is equipped towards its second end with ameans 24 for mounting a roll 26 of the vapor retarder material such thatthe axis of the roll is transverse to the length of the purlins. As thedirection of pay out of the vapor retarder material is parallel to thelength of the purlins, the roll mounting means 24 on each vertical sideframe member should be positioned to mount the roll perpendicular to thepurlin length direction. The means 24 for mounting the roll of the vaporretarder material may be either a spindle which spans the distancebetween the vertical members 22 mounted in the side members 14, 16 ormerely rotatable stub members on each of the vertical members 22 toreceive an end of the roll. Although the general goal is always to keepthe center of gravity of the device 10 low to stabilize the device, themeans 24 for rotatably mounting will be located at least one radius of afull roll above the top of the purlins, to avoid the purlins frominterfering with the pay out of the vapor retarding sheet material. Thisis because the width of the roll of web material used is at least aswide as the separation between the purlins, in order to span theintervening distance. In fact, the roll will normally be even wider toallow a preset depth to accommodate the insulation thickness.

[0015] The roll 26 will not generally be mounted on the means 24 formounting such that the roll may freely rotate. A means for braking 27should be installed to the mounting means to provide a braking bias ineither possible direction of rotation. Although the device itself isdesigned for movement in only one direction and so the roll willnormally pay off the web in a direction consistent with that movement,it has been determined that external forces such as wind can also pay asignificant factor in the operation of the device. The failure toaccount for rotation in either direction can easily result in the webfreely rotating on the mounting means and not maintaining the web in ataut position as it is payed off and guided toward the purlins. In thespecific embodiment illustrated in the Figures, the braking means 27 isa spring biased belt which passes around the mounting means.

[0016] In preferred embodiments of the device 10, there will be a meansprovided to align and guide the edges of the payed out web 30 ofmaterial as the web leaves the roll and moves toward the purlins. In theparticular embodiment disclosed in the figures, the web is payed out ina counterclockwise manner, that is, over the top of the roll 26,directly down to and around roller 29 and towards the aft end 31 of thedevice in a direction essentially parallel with the top surface of thepurlins. The means for guiding the web will be attached to the sidemembers 14, 16, and will provide a course through which the web 30 willbe fed. At an aft end 31 of the device 10, each of the side members 14,16 has a roller 32 extending from it into the intervening space betweenthe side members. As shown in the accompanying figures, the rollers 32are slidably mounted along a shaft 34 running between the side members,but it would also be possible to cantilever the rollers into theintervening space from the inner surfaces of the side members. Therollers 32 each have an enlarged flange 36 on the side distal from theside member. When positioned on the purlins, these flanges 36 may beadjusted to bear slightly against the facing surfaces of the purlins.The flanges 36 have the dual purpose of aligning and holding the devicein a parallel course as it moves along the axial direction of thepurlins and pushing the vapor retarder web downwardly between thepurlins to provide a preset depth for accommodating the depth of theinsulation to be placed thereacross. A locking clamp 38 associated witheach roller 32 allows the roller to be fixed in position on the shaft 34at a width appropriate to the purlin spacing.

[0017] The device 10 is also provided with a means 40 for dispensing anadhesive such that the adhesive is applied either to the top surface ofthe purlin or to the surface of the web which will be applied to thepurlin. In one aspect of the embodiments, the means 40 dispenses theadhesive directly onto the vapor retarder web along its side edges whilethe web 30 is still on the roll 26. In these embodiments of theinvention, the adhesive used is a double-faced tape 41 provided in aroll form, although some embodiments would allow the use of a liquidadhesive provided that such a liquid adhesive would be relativelyfast-setting. One dispensing means 40 for such a tape 41 is a mountingmeans which allows a roll of the tape to be positioned onto each of theside edges of the web 30 while it is still on the roll 26, where thetape is payed out and guided onto the web with sufficient pressure toadhere the pressure sensitive adhesive on a first side of the tape tothe surface of the web. The tape 41 is guided onto the web 30 to lie ina line which will correspond to the longitudinal axis of the purlin whenthe web is guided onto the purlin. If a release lining is provided onthe second side of the tape, that is, the side which faces upwardlyafter the first side has been attached, then means should be provided toremove this release lining after the first side is adhered to the purlinsurface. In a particular embodiment, the web 30 of film is generallydrawn off of the roll 26 in a counterclockwise manner over the top ofthe roll 26, straight downwardly to roller 29 and then essentiallystraight aft towards the aft end of the device, at which it is affixedto the purlins. For this reason, the means 40 for dispensing theadhesive 41 is positioned generally below and behind the payed out web.The dispensing means 40 is preferably mounted to the base 12, so that itmay be located directly above the purlin to which the web is to beadhesively engaged. As with the web roll 26, there is a need to raise itabove the level of the purlin to allow the double-sided tape 41 to payoff of the roll from which it is dispensed. In preferred embodiments ofthe invention, the web 30 will be held relatively tautly while theadhesive 41 is being applied, to assure good adhesion. As recited above,a roller 32 positioned atop the web 30 at the point of contact with thepurlin top surface is very useful in pressing the web down into contactwith the purlin so that the exposed adhesive on the second side of thetape is adhered to the top surface of the purlin. If, as is clearlypreferred, the web or sheet has a width essentially equal or greaterthan the spacing between the outside edges of the purlins, thelongitudinal edges of the web or sheet will lie generally atop theoutside edges of the adjacent purlins.

[0018] Although the [preferred] embodiments of the invention asdescribed above place the adhesive first on the payed out web and thenadhere the web to the purlin (in a manner unlike that taught by Ward'552, where the adhesive is placed on the purlin), it is certainlypossible to alternatively make the first adhesion of the double-sidedtape to the top surface of the purlin and then to bring the web edgesinto adhesively engagement, which is the method of Ward '552. Such adevice is described later in this specification.

[0019]FIG. 3 illustrates use of the device on roofing surface. Thedevice 10 of the present invention would be used by positioning andaligning the device on a pair of adjacent purlins 102, 104 at a roofingtermination, where a transverse support member running between theadjacent purlins is available. An adhesive, preferably the sameadhesive, such as tape 41 used with the device, is placed along the topsurface of the transverse support member and the payed out end of theweb or sheet 30 of vapor retarder material is adhered to the top of thetransverse support member. If the adhesive to be used on the web is alsoa tape or roll 41, the payed out end of such roll is adhered to the sideedge of the web. Of course, this is done on both of side edges, so thatthe vapor retarder web or sheet 30 has its payed out end adhered notonly on the payed out end, but also along each longitudinal edge. Thedevice 10 is now urged outwardly onto the purlins 102, 104 by the user.Rollers 32, 44 on the device support the device atop the purlins andflanges 36 on the rollers may be used to guide the rollers along theedges of the purlins, assuring a straight traverse. Because the purlinsmay not be in exact parallel relationship, it is considered relativelyimportant that the base 12 be provided with at least oneoutwardly-biased spring-loaded vertical roller 50, where the rollerengages the purlin edges toward the front of the device so that thedevice will cleanly track the purlins even if the purlins are not inexact parallel relationship. To achieve this objective, thespring-loaded rollers 50 should have about one to two inches of playavailable for adjusting the tracking of the device on the purlins. Apush rod or bar (not shown) can be used to push the device 10 out ontothe purlins, typically at a distance of six feet or so at a time. Thepush rod is not affixed to the device 10, but should be adapted at itsdistal end to be received by the aft end 31 of the device 10. Aparticularly good spot for pushing the device is the rear cross member18. The adhesion of the web 30 to the top surface of the purlin pays outthe sheet in a secure manner and the guiding means continues to makeadhesive contact of the web with the purlin as the device moves.

[0020] In the preferred use of the devices, a plurality of the deviceswill be set out on the purlins to be covered with the vapor retarderfilm. These devices will comprise essentially two sets. The first set,comprising devices 10 and 110 in FIG. 3, will straddle a first set ofalternating intervening spaces 200, 202 between the purlins. In thiscase, device 10 straddle purlins 102, 104 and device 110 straddlespurlins 104, 108. The second set, represented by a single device 210 inFIG. 3, will straddle the second set of alternating intervening spacesnot covered by the first set. In FIG. 3, this alternating space 204 isshown as being between purlins 104 and 106. If the first set of deviceshas a slight lead over the second set, the second set of devices will beplacing the adhesive tape and vapor retarder not directly on thepurlins, but instead atop of the tape and vapor retarder already on thepurlins from the first set, resulting in the type of overlapping jointtaught by Ward '552. In operation each of the first set devices 10, 110is advanced a short distance, typically six to ten feet, on the purlinsand the second set of devices 210 is advanced until the front ends 43 ofthe second set devices are up to the aft ends 31 of the first setdevices. At this point, insulation 300 and roofing 302 is secured to thesection newly covered by the vapor retarder by laying the insulation androofing in the transverse method described elsewhere in thisspecification. Once the insulation and roofing are in place, the firstand second sets of devices are again advanced a short distance and theprocedure repeats itself. At the opposite end of the purlin, an adhesivemay be used to adhere the transverse edge of the web to a secondtransverse support member at that roof termination. If the web isinsufficiently long to span the length of the purlins, the end of theprior web used may be used as the transverse support member for adheringthe leading edge of a new sheet or web of the vapor retarder material.

[0021] It is also known to the inventors that the two sets of devices asshown in FIG. 3 can be used without deploying adhesive onto the webdispensed by the devices 10,110 in the first or lead set. When this isdone, the roller 32 toward the aft end of the lead or first set ofdevices effectively holds the web onto the purlin tops until the secondor following set 210 may pass over the web and adhesively contact a webfrom the second set of devices atop the web from the first set ofdevices, resulting in the overlapping seam. By doing this, the webs arenot directly applied to the purlins, so there is some flexibility inmovement of the vapor retarder layer consisting of overlapping parallelstrips of web over the purlin tops, which is found to be useful inapplying insulation over the vapor retarder layer. Of course, it will behighly desirable to adhere the outermost webs to the outermost purlinson each side of the roofing surface, so that the entire periphery of thesheet is adhered directly to the purlin tops.

[0022] While the above-described methods are the preferred methods ofusing the device, it will be clear to one of skill in this art that asingle device may be used in passes across the entire length of thepurlins to lay down the vapor retarder, although this is clearly not thepreferred method of use.

[0023] In addition to the features already described, there are otherfeatures which are considered useful to proper operation of the presentinvention. One of these features is to provide the device 10 with adoctor blade 42 and/or squeegee arrangement for preparing the topsurface of the purlin by removing moisture or other foreign substanceson the purlin top surface just prior to adhesively placing the web ontothe purlin top surface. This feature may be disengaged or pivoted out ofservice in passes across a purlin which has already been covered by oneply of the adhesive and the vapor retarder, in order to prevent damageto the retarder sheet. Such a cleaning arrangement would be mounted fromthe base, preferably at the fore or front end 43 of the device 10. Itmay also be useful to place adjustable, vertically oriented guiderollers 44 on the side members 14, 16, a cross-shaft or a cross member18 to ride along and bear lightly against the inside or outside edge ofthe purlins, to keep the device tracking along the purlin as it movestherealong. In even further embodiments of the invention, the verticalmember 22 for providing a mounting point for the roll of vapor retardermay be mounted to the side member 14, 16 in a removable or collapsiblefashion so that the device may be easily transported. In a yet furtherembodiment of the invention, the cross members 18 connecting the sidemembers 14, 16 and spanning the space between the purlins to be coveredby the vapor retarder material will be easily removable so that a device10 may be adjusted by replacement of the cross members to accommodatedifferent purlin spacings and to allow the device to be disassembled foreasier transport.

[0024] In some uses of the device, it will be preferred to assemble thedevices at a staging site and to transport them not only assembled, butwith the correct lengths of web and with the rollers preset at thepurlin spacings. The assembled devices may be easily lifted in thisassembled condition onto the roof and used. In other uses, the devicesmay be assembled and set up on the roof at the time of use. As statedabove, some applications of the device and method of the presentinvention are best achieved by direct placing the adhesive onto thepurlin top surface or onto an overlapping edge of an adjacent web whichhas previously been adhered to the top surface of the purlin. In suchapplications, there is no particular need or desire to mount the roll 26containing the vapor retarder web or film 30 above the purlin topsurface on the device itself. In the roofing situations commonlyencountered, it is often desirable to keep the overall height and centerof gravity of the devices being used as low as possible to providestability and enhance the safety of the workers applying the vaporretarder web.

[0025] A device 410 for practicing this latter aspect of the presentinvention is shown in FIGS. 4 and 5; FIG. 4 showing a side elevationview from the right side of the device while it is applying a vaporretarder web 30 and FIG. 5 showing a top plan view without the web 30.The device 410 comprises a base or carriage member 412 which ispreferably rectangular and which has a width sufficient to span a pairof spaced apart purlins, and, in fact, to extend outwardly beyond theedges of the purlins. The base 412 shown in FIG. 4 has a pair ofparallel side members 414, 416 which are positioned parallel to theadjacent purlins upon which the device 410 will be moved. Connecting theside members 414, 416 are at least two cross members 418, which hold theside members in their parallel spaced apart position. Although the crossmembers 418 will be located either slightly above the top surface of thepurlins or will actually rest upon the top surface, the side members414, 416 may have a portion pending below the top surface, so that thecenter of gravity of the device is kept low. The rectangular shape ofthe base 412 will be seen to define both a fore end 419 and an aft end431.

[0026] Unlike the prior embodiment taught in FIGS. 1-3, this embodimentis not equipped for direct mounting of the roll 26 of the vapor retardermaterial thereupon so that a longitudinal axis of the roll is transverseto the length of the purlins. Because the pay out direction of the vaporretarder material is parallel to the length of the purlins, the roll 26may be laid directly atop the purlins at the aft end 431 of the device,in a manner such that the roll 26 and the device 410 co-act with eachother even while there is not physical linkage or attachment of the rolland the device. In fact, as will be described, impetus applied directlyto the roll 26 to cause pay out of the web on the roll is used to pushthe device 410 forward, that is, in the direction towards the fore end419 of the device. One of the cross members 418 is provided with atleast two different attachments for assisting in the transfer of forwardimpetus from the roll 26 to the device 410. The first of theseattachments is at least one roller assembly 450 mounted on the crossmember This is because the width of the roll of web material used is atleast as wide as the separation between the purlins, in order to spanthe intervening distance. In fact, the roll 26will normally be evenwider to allow a preset depth to accommodate the insulation thickness.

[0027] The roll 26 will not generally be mounted on the means formounting as used in the first embodiment. A means for braking may beinstalled to the device 410 to provide a braking bias in either possibledirection of movement of the device rotation. Although the device 410itself is designed for movement in only the fore direction and the roll26 will normally restrain movement in the aft direction, it has beendetermined that external forces such as wind can also pay a significantfactor in the operation of the device.

[0028] Because the web 30 on the roll 26 is positioned aft of the device410 and not onboard as in the dirst embodiment device 10, there is notneed to provide a means to align and guide the edges of the payed outweb of material as the web leaves the roll and moves toward the purlins.In the particular embodiment disclosed in the figures, the web 30 ispayed out in a counterclockwise manner, that is, over the top of theroll 26, directly down and onto the purlin surface P. At an aft end 31of the device 10, each of the side members 14, 16 has a roller 32extending from it into the intervening space between the side members.As shown in the FIGS. 4 and 5, the rollers 32 are slidably mounted alonga shaft 34 running between the side members, but it would also bepossible to cantilever the rollers into the intervening space from theinner surfaces of the side members. The rollers 32 each have an enlargedflange 36 on the side distal from the side member. When positioned onthe purlins, these flanges 36 may be adjusted to bear slightly againstthe facing surfaces of the purlins. The flanges 36 have the purpose ofaligning and holding the device in a parallel course as it moves alongthe axial direction of the purlins. A locking clamp 38 associated witheach roller 32 allows the roller to be fixed in position on the shaft 34at a width appropriate to the purlin spacing.

[0029] The device 410 is also provided with a means 40 for dispensing anadhesive such that the adhesive is applied directly to the top surface Pof the purlin. In this embodiment of the invention, the adhesive used isa double-faced tape 41 provided in a roll form, although someembodiments would allow the use of a liquid adhesive provided that sucha liquid adhesive would be relatively fast-setting. One dispensing means40 for such a tape 41 is a mounting means which allows a roll of thetape to be positioned onto each of the top surfaces P of a pair ofadjacent purlins with sufficient pressure to adhere the pressuresensitive adhesive on a first side of the tape to the top purlinsurface. If a release lining is provided on the second side of the tape,that is, the side which faces upwardly after the first side has beenattached, then means should be provided to remove this release liningafter the first side is adhered to the purlin surface. In thisparticular embodiment, the web 30 of film is generally drawn off of theroll 26 in a counterclockwise manner over the top of the roll 26,straight downwardly onto the purlin top surface P, at which point theexposed face of the double-sided adhesive tape 41 adheres to it. Thedispensing means 40 is preferably mounted to the base 412, so that itmay be located directly above the purlin to which the web is to beadhesively engaged. As recited above, a roller 32 at the point ofcontact with the purlin top surface is very useful in pressing the tapedown into contact with the purlin.

[0030] In addition to the features already described, there are otherfeatures which are considered useful to proper operation of the presentinvention. One of these features is to provide the device 410 with adoctor blade 42 and/or squeegee arrangement for preparing the topsurface of the purlin by removing moisture or other foreign substanceson the purlin top surface just prior to adhesively placing the web ontothe purlin top surface. This feature may be disengaged or pivoted out ofservice in passes across a purlin which has already been covered by oneply of the adhesive and the vapor retarder, in order to prevent damageto the retarder sheet. Such a cleaning arrangement would be mounted fromthe base, preferably at the fore or front end 419 of the device 410. Itmay also be useful to place adjustable, vertically oriented guiderollers 444 on the side members 414, 416, a cross-shaft or a crossmember 418 to ride along and bear lightly against the inside or outsideedge of the purlins, to keep the device tracking along the purlin as itmoves therealong.

[0031] In some uses of the device, it will be preferred to assemble thedevices at a staging site and to transport them not only assembled, butwith the correct lengths of web and with the rollers preset at thepurlin spacings. The assembled devices may be easily lifted in thisassembled condition onto the roof and used. In other uses, the devicesmay be assembled and set up on the roof at the time of use.

[0032] While the preferred embodiment is described as required under thePatent Laws, the scope of the invention is not to be determined by thepreferred embodiment, but instead by the accompanying claims.

What is claimed is:
 1. A device for applying a vapor retarder film atop a pair of adjacent parallel spaced apart purlins having a top surface in a roofing system having a plurality of the purlins with an interval between the purlins, comprising: a base having a fore end and an aft end with a pair of side members which are provided with means for moving the base along the length of the pair of purlins such that the side members are in a fixed spaced apart relationship wider than the spacing between the pair of purlins; a vertical member attached to each of the side members, the vertical members provided with a means for mounting a web of the vapor retarder film on a roll above an adjacent pair of the spaced apart purlins; means for dispensing a continuous line of adhesive along an edge of a surface of the web of vapor retarder film; and means for paying out and guiding the vapor retarder film such that the edge having the line of adhesive is in adhesive engagement with the top surface of the purlins and the film sealingly spans the interval between the adjacent purlins.
 2. The device of claim 1 wherein the mounting means comprises a spindle having first and second ends and a pair of mounts for receiving one end of the spindle, the mounts being affixed to the vertical members.
 3. The device of claim 1 wherein the mounting means comprises first and second stub members for receiving an end of the roll holding the film, one of the stub members affixed to each of the vertical members.
 4. The device of claim 1 wherein the line of adhesive is provided by a roll of double-sided adhesive tape and the means for dispensing the line of adhesive comprises a mount for positioning the roll above the top of the web as it is payed out, a guide for aligning the tape into adhesive engagement of the edge of the web surface, and a means for removing a release liner from a second side of the tape.
 5. The device of claim 1 wherein the line of adhesive is provided by a container of liquid adhesive and the means for dispensing the line of adhesive comprises a mount for positioning the container above the edge of the web and a nozzle for dispensing a bead of the adhesive in a continuous line onto the edge of the web.
 6. The device of claim 1 wherein the line of adhesive is placed on the web edge immediately forward of proximate to the engagement of the web to the purlin.
 7. The device of claim 1 wherein the base is further provided at the fore end thereof with a means for preparing the top surface of the purlin prior to placement of the web of film thereon.
 8. The device of claim 1 wherein the means for moving the base along the length of the pair of purlins comprises at least one roller.
 9. A method for covering a roof surface with a continuous layer of a vapor retarder material in adhesive contact with a periphery of the roof surface, the roof surface comprising a plurality of parallel spaced-apart roof support members, with the first and last of the roof support members defining a first and second side of the roof periphery and a pair of transverse members defining a third and a fourth side of the periphery, the continuous layer comprising a plurality of webs of the vapor retarder material such that each web is in parallel overlapping adhesive contact with at least one adjacent web and the roof periphery, said method comprising the steps of: a) placing a first set of web applying devices atop pairs of adjacent roof support members at the transverse member defining the third side of the roof periphery such that the first of the first set of devices spans an intervening space between the first and second roof support members, the second of the first set of devices spans the intervening space between the third and fourth roof support members, and so forth until the last of the first set of devices spans the intervening space between the next to last and last roof support members; b) adhering an end of the web of each of the first set of web applying devices to the third side of the roof periphery and adhering a side edge of the web corresponding to the first and last roof support members to the roof support member; c) advancing each of the first set of web applying devices an incremental distance toward the fourth side of the roof periphery along the roof support members, paying out the web atop the roof support members as the devices advance; d) placing a second set of web applying devices atop pairs of adjacent roof support members to span the intervening spaces between roof support members not spanned by the first set of the web applying devices; e) adhering an end of the web of each of the second set of web applying devices to the third side of the roof periphery and adhering each side edge of the web to the webs payed out atop the roof support members by the first set of devices in an overlapping adhesive seal; f) advancing each of the second set of web applying devices an incremental distance toward the fourth side of the roof periphery along the roof support members, paying out the web into overlapping adhesive seal atop the web payed out by the first set of devices, keeping a front end of each of the second set of devices behind a rear end of the adjacent first set of devices; and g) repeating steps c) and f) sequentially in incremental steps until the first and second set of devices reach the fourth side of the roof periphery and the web on each device is adhered to the fourth side of the roof periphery.
 10. In combination with a web of a vapor retarder film mounted on a roll which traverses a pair of adjacent parallel spaced apart purlins having a top surface in a roofing system having a plurality of the purlins with an interval between the purlins, a device for adhering the film web to the purlins to sealingly span the interval, the device comprising: a base having a fore end and an aft end with a pair of side members which are provided with means for moving the base along the length of the pair of purlins such that the side members are in a fixed spaced apart relationship wider than the spacing between the pair of purlins; means for dispensing a continuous line of adhesive directly along a top surface of the purlin, said means mounted on the base; and means for receiving a forward thrust force applied through the web for advancing the base, such means mounted on the aft end of the base, the forward thrust force serving to pay out and guide the vapor retarder film web directly from the roll to the purlin such that an edge of the film web is placed into adhesive engagement with the top surface of the purlins.
 11. The device of claim 10 wherein the line of adhesive is placed on the web edge immediately forward of an engagement point of the web to the purlin.
 12. The device of claim 10 wherein the base is further provided at the fore end thereof with a means for preparing the top surface of the purlin prior to placement of the web of film thereon.
 13. The device of claim 1 wherein the means for moving the base along the length of the pair of purlins comprises at least one roller. 